Saprolegnia Research Articles

Saprolegniosis in aquaculture and how to control it?

AbstractSaprolegniosis, also called water mould, induces a cotton or wool‐like white growth on fish skin. It can kill fish at all stages of life, from eggs to adults. It is caused by oomycetes from the genus Saprolegnia and causes fish mortality and huge financial losses to fish farms and hatcheries. Saprolegnia species are endemic and ubiquitous in all freshwater habitats around the world. The exposing factors for saprolegniosis are still largely unknown, but stressors such as temperature shocks, poor water quality, handling and high fish density have been associated with outbreaks. For decades, malachite green was the most effective treatment against Saprolegnia infection, but it has been banned due to its carcinogenic and toxic effects. This has forced farmers to use alternative disinfection methods against Saprolegnia infection, such as hydrogen peroxide, formalin, Bronopol, NaCl, acetic acid and ozone, although many may have safety concerns or are impractical to use. This has led to the investigation of plant‐based compounds with antifungal and antibacterial properties against saprolegniosis. These include extracts of certain herbs, onion, garlic, extracts of the plant Chrysanthemum, essential oils of Eryngium campestre, Mentha piperita, Cuminum cyminum and Thymus linearis, which include a variety of phenolic compounds and fatty acids with antifungal properties. This review combines the current knowledge regarding the predisposing factors to Saprolegnia infections and current methods to prevent and treat them, including those under further research. Thus far, many compounds have been tested and studied, but an effective, suitable and safe compound to treat Saprolegnia infection remains to be found.

Frequent Oomycotic Infections in Eggs of Cultured Species

In aquaculture farms, incubation is a one crucial stage, as frequently shows high percentage of mortality. In fish and amphibians, egg oomycosis is a common infection during the early stages of embryonic development. Infection is usually promoted by unfertilized or damaged eggs that provide a medium for the zoospores to establish and grow, resulting in colonization and spread of the infection to nearby viable eggs. Numerous essential oils have been shown to have anti-oomycotic activity and to inhibit production and spore germination of Oomycetes species of the order Saprolegniales

Prevalence and genetic analyses of Saprolegnia strains isolated from Nile tilapia farms at northern Egypt

This study was undertaken to investigate saprolegniasis outbreaks in Nile tilapia farms at northern Egypt and its linkage to the water quality parameters, besides, their genetic diversity across different farms and the induced ultrastructural lesions. Water quality parameters were recorded and a total of 200 Nile tilapia showing saprolegniasis like signs were collected from December 2017–March 2018 from three different regions at El-Manzala, Gamasa, and El-Sirw, located at northern Egypt. A significant increase was observed in salinity, where El-Manzala showed the lowest level lowest 0.25 g/L followed by Gamasa and El-Sirw at salinity levels of 3.5 g/L, and 2.15 g/L, respectively. The prevalence of saprolegniasis showed significant variations between different regions (P < 0.05) and across different months (P < 0.0001). El-Manzala showed the higher prevalence (90.91%, 100/10) compared to El-Sirw (77.5%, 31/40), but no significant prevalence changes were observed between Gamasa (80%, 40/50) compared to both El-Manzala and El-Sirw regions (P > 0.05). Similarly, monthly prevalence where significantly increased during all months, but March; and Saprolegnia isolates were highly recovered from skin and fins followed by gills. All strains isolated were morphologically classified in the genus Saprolegnia, and they were identified presumptively as S. parasitica/diclina, S. ferax, and S. litoralis according to their sexual characteristics. The genetic variation among the 23 Saprolegnia isolates were investigated using RAPD-PCR, an approach has not been done yet for Nile tilapia saprolegniasis, and results revealed isolates split into two distinct clades using based on genetic similarities, demonstrating that there is genetic diversity among the isolates. Clade I contains seven isolates out of 23 (30.4%), whereas clade II contains sixteen isolates out of 23 (69,5%). Ultrastructural examination revealed sexual and asexual stage of Saprolegnia with numerous mycelia, besides skin necrosis and ulceration, however the attachment components, such as appressoria and hooked hairs were not observed. Our results provide a better overview of the Saprolegnia outbreaks in different regions and their association to the risk factors contributing to Saprolegnia pathogenicity, and the ultrastructure alterations induced in fish skin confirming the disease. Further, for the first time a genetic diversity of Saprolegnia isolates among different localities has been explored in Nile tilapia.

Impact of abiotic factors and husbandry on saprolegniosis in salmonid farms

Oomycetes of the genus Saprolegnia are widespread in freshwater environment and are among the main pathogens causing economic losses in salmonid aquaculture.Infections by mycotic agents in fish farming are generally considered to result from chronic stress and poor fish condition associated with water quality problems, adverse environmental conditions, frequent/rough/incorrect handling, concurrent infections, physiological changes associated with reproduction and immunocompromised animals.To identify risk factors for Saprolegnia infections in trout and Atlantic salmon farming, longitudinal studies were carried out in different Italian, Spanish, and Scottish fish farms. Prevalence of saprolegniosis and fish mortality were monitored over time and statistically analysed with respect to husbandry and environmental factors.Overall, statistical results by production cycle (trout vs salmon farming) and by country indicate that the prevalence of Saprolegnia may be influenced by peculiarities of the culture system and farming environment. Nevertheless, a specific set of parameters, including lower water temperature, and handling procedures increased Saprolegnia prevalence in all the considered farms. Particularly, in trout farms Saprolegnia infections represented an important contribution to mortality, and prevalence was influenced by water temperature and pH, and by fish density within the tanks. Similarly, temperature and water quality were the main factors influencing the prevalence of Saprolegnia in Atlantic salmon farms. Moreover, molecular analyses confirmed the role of S. parasitica as the main pathogenic oomycete in trout and salmon farming in the considered countries. The identification of risk factors for introduction and increase of Saprolegnia infection in fish farms will allow the correct design of biosecurity and pathogen control strategies.

Anti-oomycete Activity of Chlorhexidine Gluconate: Molecular Docking and in vitro Studies.

Saprolegniosis is one of the most catastrophic oomycete diseases of freshwater fish caused by the members of the genus Saprolegnia. The disease is responsible for huge economic losses in the aquaculture industry worldwide. Until 2002, Saprolegnia infections were effectively controlled by using malachite green. However, the drug has been banned for use in aquaculture due to its harmful effect. Therefore, it has become important to find an alternate and safe anti-oomycete agent that is effective against Saprolegnia. In this study, we investigated the anti-oomycete activity of chlorhexidine gluconate (CHG) against Saprolegnia. Before in vitro evaluation, molecular docking was carried out to explore the binding of CHG with vital proteins of Saprolegnia, such as S. parasitica host-targeting protein 1 (SpHtp1), plasma membrane ATPase, and TKL protein kinase. In silico studies revealed that CHG binds with these proteins via hydrogen bonds and hydrophobic interactions. In an in vitro study, the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of CHG against S. parasitica were found to be 50 mg/L. Further, it was tested against S. australis, another species of Saprolegnia, and the MIC and MFC were found to be 100 and 200 mg/L, respectively. At 500 mg/L of CHG, there was complete inhibition of the radial growth of Saprolegnia hyphae. In propidium iodide (PI) uptake assay, CHG treated hyphae had bright red fluorescence of PI indicating the disruption of the cell membrane. The results of the present study indicated that CHG could effectively inhibit Saprolegnia and hence can be used for controlling Saprolegniasis in cultured fish.

Saprolegnia atlantica sp. nov. (Oomycota, Saprolegniaceae) from Brazil, and new synonymizations and epitypifications in the genus Saprolegnia

Saprolegnia atlantica sp. nov. (Oomycota, Saprolegniaceae) from Brazil, and new synonymizations and epitypifications in the genus Saprolegnia

Development and comparison of loop-mediated isothermal amplification with quantitative PCR for the specific detection of Saprolegnia spp.

Saprolegniasis is an important disease in freshwater aquaculture, and is associated with oomycete pathogens in the genus Saprolegnia. Early detection of significant levels of Saprolegnia spp. pathogens would allow informed decisions for treatment which could significantly reduce losses. This study is the first to report the development of loop-mediated isothermal amplification (LAMP) for the detection of Saprolegnia spp. and compares it with quantitative PCR (qPCR). The developed protocols targeted the internal transcribed spacer (ITS) region of ribosomal DNA and the cytochrome C oxidase subunit 1 (CoxI) gene and was shown to be specific only to Saprolegnia genus. This LAMP method can detect as low as 10 fg of S. salmonis DNA while the qPCR method has a detection limit of 2 pg of S. salmonis DNA, indicating the superior sensitivity of LAMP compared to qPCR. When applied to detect the pathogen in water samples, both methods could detect the pathogen when only one zoospore of Saprolegnia was present. We propose LAMP as a quick (about 20-60 minutes) and sensitive molecular diagnostic tool for the detection of Saprolegnia spp. suitable for on-site applications.

Chemical Analysis and In Vitro Bioactivity of Essential Oil of Laurelia sempervirens and Safrole Derivatives against Oomycete Fish Pathogens.

In this study, the essential oil (EO) from Laurelia sempervirens was analyzed by GC/MS and safrole (1) was identified as the major metabolite 1, was subjected to direct reactions on the oxygenated groups in the aromatic ring and in the side chain, and eight compounds (4 to 12) were obtained by the process. EO and compounds 4–12 were subjected to biological assays on 24 strains of the genus Saprolegnia, specifically of the species 12 S. parasitica and 12 S. australis. EO showed a significant effect against Saprolegnia strains. Compound 6 presents the highest activity against two resistant strains, with minimum inhibitory concentration (MIC) and minimum oomyceticidal concentration (MOC) values of 25 to 100 and 75 to 125 µg/mL, respectively. The results show that compound 6 exhibited superior activities compared to the commercial controls bronopol and azoxystrobin used to combat these pathogens.

Identification and molecular characterization of oomycete isolates from trout farms in Croatia, and their upstream and downstream water environments

Oomycetes from the genus Saprolegnia are opportunistic pathogens that cause significant losses in salmonid aquaculture. Despite this, studies reporting dominant Saprolegnia species in different fish farming facilities, as well as analyses of their spreading to natural environments, are still scarce. In this study, we have for the first time identified oomycete species present in four different trout farms in Croatia. We have collected 220 oomycete isolates, both from affected tissue (46 in total: adult trout - 28, eggs - 13, and alevins - 5) and from water (174 in total: in the fish farm – 78, upstream – 50, and downstream - 46). We have used Bayesian inference to reconstruct phylogenetic relationship among the internal transcribed spacer (ITS) sequences of the collected isolates and referent strains, and determined that the isolates belonged to three different oomycete genera: Saprolegnia (64% of isolates), Pythium (35%), and Leptolegnia (1%). Saprolegnia isolates were classified into four species: S. parasitica with 53 isolates, S. australis - 52, S. delica – 25, and S. ferax – 11. Pythium and Leptolegnia isolates couldn't be identified to the species level and probably belong to so far undescribed species since their sequences didn't group with previously described species. Next, isolates from the affected tissue were mostly S. parasitica (32), while S. australis, S. delica, and S. ferax were less common (≤ 4 isolates per species). Furthermore, we used hempseed baits to capture oomycetes from water and positioned them inside the fish farms, as well as upstream (between 55 and 155 m) and downstream (between 95 and 140 m) of the fish farms. According to correspondence analysis, Saprolegnia species showed a strong association with fish farms and downstream locations, while upstream locations were associated with Pythium species, highlighting a possible role of trout farms as a source of spreading Saprolegnia species into the environment.

Detection of fish pathogen Saprolegnia parasitica in environmental DNA samples by droplet digital PCR

Oomycetes are fungal-like microorganisms parasitic towards a large number of plant and animal species. Genera from order Saprolegniales, such as Saprolegnia and Aphanomyces, cause devastating infections of freshwater animals. Saprolegnia parasitica is a widely distributed oomycete pathogen that causes saprolegniosis, a disease responsible for significant economic losses in aquaculture, as well as declines of natural populations of fish and other freshwater organisms. Despite its negative impact, no monitoring protocol for S. parasitica has been established to date. Thus, we aimed to develop a droplet digital PCR (ddPCR) assay for the detection and quantification of S. parasitica in environmental DNA samples. Saprolegnia parasitica-specific primers were designed to target internal transcribed spacer region 2 (ITS 2), based on the alignment of ITS sequences of S. parasitica and a range of Saprolegnia spp., as well as other oomycetes. The specificity of primers was tested using genomic DNA of S. parasitica (as positive control) and DNA of non–S. parasitica oomycete isolates, as well as trout/crayfish DNA (as negative control). The primers specifically amplified a segment of the ITS region of oomycete pathogen S. parasitica, while no amplification (i.e. no positive droplets) was obtained for closely related Saprolegnia spp. (e.g. Saprolegnia sp. 1 and S. ferax) and other more distantly related oomycetes. Next, the limit of detection (LOD) of the assay was established by using serial dilutions of the S. parasitica genomic DNA. The determined sensitivity of the assay was high: LOD was 15 fg of pathogen’s genomic DNA per µL of the reaction mixture. Assay performance was further assessed with environmental DNA samples isolated from water from the trout farms and natural environments, as well as (ii) biofilm from the host surface (swab samples). Water samples were collected from 21 different locations in Croatia, while swab samples were collected from S. parasitica host/carrier species: (i) skin and eggs of the rainbow trout (Oncorhynchus mykiss Walbaum, 1792) and brown trout (Salmo trutta Linnaeus, 1758), and (ii) cuticle of signal crayfish (Pacifastacus leniusculus Dana, 1852) and narrow clawed crayfish (Pontastacus leptodactylus Eschscholtz, 1823). Samples were classified into agent levels A0 to A6, depending of the number of S. parasitica ITS copies per ng of total DNA. Saprolegnia parasitica was detected in 76 % of water samples (16/21) and the range of pathogen’s ITS copies in positive samples was between 0.02 and 14 copies/ng of total DNA (agent levels A1 to A3). Regarding the swab samples, S. parasitica load was significantly higher in diseased trout than in those with healthy appearance: 9375 vs 3.28 S. parasitica copies/ng of total swab DNA (average agent level A6 vs. A2, respectively). Despite the fact that none of the sampled crayfish had signs of infection, the pathogen was detected in all tested cuticle swabs. Swabs of P. leniusculus, a known S. parasitica host, had significantly higher S. parasitica load than swabs of P. leptodactylus, S. parasitica carrier: 390 vs 83 S. parasitica copies/ng (agent level A5 vs. A4, respectively). In conclusion, our results demonstrate the applicability of the newly developed ddPCR assay in monitoring and early detection of S. parasitica in aquaculture facilities and natural freshwater environments. This would help in a better understanding of S. parasitica ecology and its effects on the host populations.

Registry of saprolegniose in fish cultivated in the world: a compilation of data

Saprolegniosis is a mycological disease that causes significant economic losses in fish culture and can be considered an obstacle to the development of world fish farming. Thus, we aimed to identify which species of fish cultivated in the world have been associated with fungi of the genus Saprolegnia. The research deals with a bibliographical survey that contemplates articles published between 2007 and July of 2017. We found a relationship of saprolegniose with fish species: Oncorhynchus mykiss, Salmo trutta, Oncorhynchus tshawytscha, Labeo rohita, Pterophyllum scalare, Ctenopharyngodon idella, Sander lucioperca, Pelteobagrus fulvidraco, Oreochromis niloticus, Odonthestes bonariensis, Odonthestes humensi e Catla catla. The oomycetes found were: Saprolegnia ferax, Saprolegnia parasitica, Saprolegnia australis, Saprolegnia diclina, Saprolegnia delica, Saprolegnia glomerata, Saprolegnia terrestres, Saprolegnia uliginosa, Saprolegnia unispora, Saprolegnia hypogyna and Saprolegnia longicaulis. The species S. ferax and S. parasitica were the fungi that presented the highest infection register, mainly in salmonids. O. mykiss, S. salar and S. trout were the fish with more studies related to saprolegniose, because they are species that have great market importance in the world fish farming scenario. Despite the great importance of the species O. niloticus in the world fish culture, we observed the specie in only one article in this research, which may be related to the high resistance of the species to diseases and to the lack of research funding to identify this type of infection. It was not possible to compare the host - etiological agent among the fish, since many of the studies considered in the research did not have the purpose of identifying the pathogen.

Identification of Growth Inhibitors of the Fish Pathogen Saprolegnia parasitica Using in silico Subtractive Proteomics, Computational Modeling, and Biochemical Validation.

Many Stramenopile species belonging to oomycetes from the genus Saprolegnia infect fish, amphibians, and crustaceans in aquaculture farms and natural ecosystems. Saprolegnia parasitica is one of the most severe fish pathogens, responsible for high losses in the aquaculture industry worldwide. Most of the molecules reported to date for the control of Saprolegnia infections either are inefficient or have negative impacts on the health of the fish hosts or the environment resulting in substantial economic losses. Until now, the whole proteome of S. parasitica has not been explored for a systematic screening of novel inhibitors against the pathogen. The present study was designed to develop a consensus computational framework for the identification of potential target proteins and their inhibitors and subsequent experimental validation of selected compounds. Comparative analysis between the proteomes of Saprolegnia, humans and fish species identified proteins that are specific and essential for the survival of the pathogen. The DrugBank database was exploited to select food and drug administration (FDA)-approved inhibitors whose high binding affinity to their respective protein targets was confirmed by computational modeling. At least six of the identified compounds significantly inhibited the growth of S. parasitica in vitro. Triclosan was found to be most effective with a minimum inhibitory concentration (MIC100) of 4 μg/ml. Optical microscopy showed that the inhibitors affect the morphology of hyphal cells, with hyper-branching being commonly observed. The inhibitory effects of the compounds identified in this study on Saprolegnia’s mycelial growth indicate that they are potentially usable for disease control against this class of oomycete pathogens. Similar approaches can be easily adopted for the identification of potential inhibitors against other plant and animal pathogenic oomycete infections.

Water Molds of the Order Saprolegniales (Oomycota) in Association with Fish and Sponge Species from Lake Baikal

The first molecular identification and comparison of the spectrum of representatives of the order Saprolegniales (Oomycota) in sponges and on the outer skin of fishes under native conditions of Lake Baikal and under the conditions of aquarium exhibits were conducted. A similar spectrum of water molds in fish and sponges in aquarium exhibits and the presence in sponges in Lake Baikal of a species close to Leptolegnia chapmanii, which is parasite in insect larvae, were found. The results of detection of representatives of the order Saprolegniales and the factors influencing the frequency of their occurrence in samples of sponges from Lake Baikal are examined.

High mortality in Bufo gargarizans eggs associated with an undescribed Saprolegnia ferax strain in the Republic of Korea

Pathogenic water molds have a significant impact on many species, especially amphibians. The genus Saprolegnia is a pathogenic oomycete restricted to aquatic and moist habitats, and its presence is strongly linked to the abundance of amphibians and fishes. We investigated the influence of Saprolegnia presence on egg mortality and egg occurrence under varying environmental conditions in the Asiatic toad Bufo gargarizans at 27 breeding sites in the Republic of Korea. We then assessed the impact of Saprolegnia on the presence of B. gargarizans at the 27 sites surveyed weekly during the B. gargarizans breeding season for 3 consecutive years. We used molecular tools to identify the water molds as belonging to an undescribed S. ferax strain. We demonstrated that the presence of S. ferax was positively associated with higher water conductivity and ponds. In addition, while S. ferax prevalence was associated with a reduction in B. gargarizans breeding activity and breeding success, we could not determine its impact on the subsequent breeding seasons. Our study highlights the potential negative effects of Saprolegnia on amphibian reproduction, although additional research is necessary to determine the relationship between Saprolegnia, its hosts and the impacts of habitat loss on amphibians.

First Record of the Water Mold Achlya bisexualis (Saprolegniaceae) Isolated from Ornamental Fish in South Africa.

The order Saprolegniales (Class Oomycota) is a group of fungus-like eukaryotic microorganisms that have been associated with infections in fish and fish eggs. Infections with microorganisms from this order are clearly evident because they have a cotton wool-like appearance. The aim of this study was to characterize and identify an oomycete that was isolated from the eye of an Orange Blotched Peacock Cichlid Aulonacara sp. A sample of cotton wool-like mycelia was isolated and single-spore isolations were conducted. Molecular characterization and phylogenetic analysis of the ITS1-5.8-ITS2 rDNA region for all isolates were used for species identification. Following molecular identification, one isolate was used to culture and characterize the reproductive structures. Physiological characterization entailed incubating the isolate on potato dextrose agar (PDA) at five different temperatures, ranging from 5°C to 25°C, to monitor growth rates. A multiple sequence alignment showed 100% similarity between all of the single-spore isolates and alignment with other Achlya bisexualis strains. Long, coarse hyphae with zoosporangia and gemmae typical of the order Saprolegniales were observed with an optimal growth rate at 25°C. The oomycete that was isolated from an Orange Blotched Peacock Cichlid was identified as A.bisexualis, the first record of this species in South Africa.

Fungal systematics and evolution : FUSE 4

Eight new species presented are Calostoma areolatum collected in Wuyishan National Park (China), Crinipellis bidens from Hubei Province (China), Lactifluus sainii from Himalayan India, Inocybe elata from Yunnan (China), Inocybe himalayensis from Pakistan. Specimens previously identified as Massalongia carnosa represent a new species, namely M. patagonica restricted to southern South America. Saprolegnia maragheica is a new oomycete species of fresh water in Maraghe (Iran). Uncispora wuzhishanensis is a new aquatic hyphomycete species. A type specimen of Raddetes turkestanicus was studied and based on this the new combination Conocybe turkestanica, is proposed. Argyranthemum frutescens is a new host for Alternaria alternata and Syzygium cumini for Phyllosticta capitalensis in India. Crepidotus ehrendorferi is confirmed for Hungary and Pluteus leucoborealis for Central Europe, and for the phytogeographical region of Carpaticum. Pseudopithomyces palmicola is shown to occur on grapevine and it is validated by adding a unique identifier. Terfezia fanfani is reported first from Algeria.

In vitro activity of chemicals and commercial products against Saprolegnia parasitica and Saprolegnia delica strains.

Oomycetes of the genus Saprolegnia are responsible for severe economic losses in freshwater aquaculture. Following the ban of malachite green in food fish production, the demand for new treatments pushes towards the selection of more safe and environment‐friendly products. In the present work, in vitro activity of ten chemicals and three commercial products was tested on different strains of Saprolegnia, using malachite green as reference compound. The compounds were screened in agar and in water to assess the minimum inhibitory concentration (MIC) and the minimum lethal concentration (MLC), respectively. Two strains of Saprolegnia parasitica and one isolate of Saprolegnia delica were tested in triplicate per each concentration. Among tested chemicals, benzoic acid showed the lowest MIC (100 ppm) followed by acetic acid, iodoacetic acid and copper sulphate (250 ppm). Sodium percarbonate was not effective at any tested concentration. Among commercial products, Virkon™S was effective in inhibiting the growth of the mycelium (MIC = MLC = 1,000 ppm). Actidrox® and Detarox® AP showed MIC = 5,000 and 1,000 ppm, respectively, while MLCs were 10‐fold lower than MICs, possibly due to a higher activity of these products in water. Similarly, a higher effectiveness in water was observed also for iodoacetic acid.

Saprolegnia parasitica Isolated from Rainbow Trout in Korea: Characterization, Anti-Saprolegnia Activity and Host Pathogen Interaction in Zebrafish Disease Model

Saprolegniasis is one of the most devastating oomycete diseases in freshwater fish which is caused by species in the genus Saprolegnia including Saprolegnia parasitica. In this study, we isolated the strain of S. parasitica from diseased rainbow trout in Korea. Morphological and molecular based identification confirmed that isolated oomycete belongs to the member of S. parasitica, supported by its typical features including cotton-like mycelium, zoospores and phylogenetic analysis with internal transcribed spacer region. Pathogenicity of isolated S. parasitica was developed in embryo, juvenile, and adult zebrafish as a disease model. Host-pathogen interaction in adult zebrafish was investigated at transcriptional level. Upon infection with S. parasitica, pathogen/antigen recognition and signaling (TLR2, TLR4b, TLR5b, NOD1, and major histocompatibility complex class I), pro/anti-inflammatory cytokines (interleukin [IL]-1β, tumor necrosis factor α, IL-6, IL-8, interferon γ, IL-12, and IL-10), matrix metalloproteinase (MMP9 and MMP13), cell surface molecules (CD8+ and CD4+) and antioxidant enzymes (superoxide dismutase, catalase) related genes were differentially modulated at 3- and 12-hr post infection. As an anti-Saprolegnia agent, plant based lawsone was applied to investigate on the susceptibility of S. parasitica showing the minimum inhibitory concentration and percentage inhibition of radial growth as 200 μg/mL and 31.8%, respectively. Moreover, natural lawsone changed the membrane permeability of S. parasitica mycelium and caused irreversible damage and disintegration to the cellular membranes of S. parasitica. Transcriptional responses of the genes of S. parasitica mycelium exposed to lawsone were altered, indicating that lawsone could be a potential anti-S. parasitica agent for controlling S. parasitica infection.

Observations and first reports of saprolegniosis in Aanaakłiq, broad whitefish (Coregonus nasus), from the Colville River near Nuiqsut, Alaska

We report the first confirmed cases (2013–2016) of saprolegniosis caused by water mold from the genus Saprolegnia in Aanaakłiq, broad whitefish (Coregonus nasus), from the Colville River near Nuiqsut, Alaska. While this mold is known to be worldwide, these instances represent the first cases in Nuiqsut and only the second instance on a single fish on the North Slope, occurring in 1980. We describe the collaborative work on monitoring this emerging disease. Because fish constitute a critical component of the diet in Nuiqsut and fishing is an integral part of Inupiaq nutritional and cultural subsistence activities overall, individual subsistence fishers, local governmental entities, and Alaska Native organizations representing Nuiqsut requested an examination of affected fish and information on possible drivers of this emerging disease. The collaborative work described here ranges from recording fishermen observations, acquiring fish and mold specimens, histopathology, and molecular identification of the mold. This work, not currently grant-funded, begins with Native observation that incorporates western scientific methods and involves local, state, and federal departments as well as for-profit and non-profit organizations. Additionally, we report the more recent (2016) observation of this disease in a second species of whitefish, Pikuktuuq, humpback whitefish (Coregonus pidschain).

Bacterial pathogens and health problems of Acipenser gueldenstaedtii and Acipenser baerii sturgeons reared in the eastern Black Sea region of Turkey.

Farming sturgeons is an economically important practice in a number of Asian and European countries. However, since it is not widely implementedin Turkey, fertilized eggs necessary for research and industrial activities are imported from Germany. Due to the interest of several fish farms in culturing sturgeon in Turkey and the lack of relevant data, this study investigated bacteria related health problems of two different sturgeon species, the diamond sturgeon (Acipenser gueldenstaedtii) and the Siberian sturgeon (Acipenser baerii). The fungal, parasitic and bacterial pathogens found in these fish were investigated until the fish reached about 3 kg of weight (3+ years). A number of bacterial disease pathogens (Acinetobacter radioresistens, some Aeromonas and Pseudomonas species and Bacillus mycoides) and parasite Trichodina sp. and fungus Saprolegnia sp. were identified in the fish. Both phenotypic and molecular characterizations of the isolated bacteria were performed. Furthermore, swim bladder and spinal problems, cannibalism, tumor growth and mechanical injuries on the external surface of the fish were observed during the study period.